1. Field of the Invention
The present invention relates to a voltage controller for an automotive alternator mounted on a vehicle and, more particularly, to a voltage controller for an automotive alternator having a switching means for controlling the supply and cutoff of exciting current supplied to a field coil of an alternator.
2. Description of the Related Art
FIG. 11 is a circuit diagram of a conventional voltage controller for an automotive alternator. Referring to FIG. 11, an automotive alternator 10 has a field coil 2, a Y-connected armature coil 3, and a rectifier 4. A main output terminal 10a of the alternator 10 is connected to the positive electrode of a battery 5, the negative electrode of the battery 5,being grounded.
A voltage: controller 60 is connected between the main output terminal 10a and a grounding terminal 10b of the alternator 10 The voltage controller 60 has an input terminal L to which the voltage of the battery 5 is applied via an ignition switch 6 and a charge lamp 7, which are interconnected in series. The voltage controller 60 has an FR terminal for monitoring the conduction rate of the field coil 2 of the alternator 10 from the ignition switch 6 via an external control unit 8.
When the ignition switch 6 is closed, the voltage from the battery 5 is applied to the L terminal via the charge lamp 7, and the voltage is applied to the FR terminal via a resistor 801 of the external control unit 8.
A comparator 108 serving as a switching means indicates a High state when a rectified output voltage from the rectifier 4, which is an AC output generated at the armature coil 3, is below a first set voltage, e.g., 14.5 v, and turns ON a field coil driving transistor 110 thereby to supply field current to the field coil 2. At this time, the current passes: via a diode 112, and the FR terminal indicates a Low state.
When the field current is supplied to the field coil 2, causing the alternator 10 to start generating power, and the output voltage of the alternator exceeds the aforesaid first set voltage, the output of the comparator 108 indicates the Low state. This causes the field coil driving transistor 110 to turn OFF, and the field current attenuates while circulating the field coil 2 and a diode 111. At this time, the FR terminal indicates the High state. Thus, the FR terminal monitors the conduction rate of the field coil 2 of the alternator 10.
The voltage controller 60 of the automotive alternator having the configuration described above includes the comparator 108 in which the first set voltage is set, and which serves as the switching means for controlling the supply and cutoff of the exciting current supplied to the field coil 2 of the alternator 10, and the FR terminal for monitoring the field coil conduction rate of the field coil 2 of the alternator 10. The output of the FR terminal is applied to the external control unit 8 so as to be used primarily for controlling the volume of intake air and the number of revolutions of an engine.
In general, when an electric equipment load, such as a head light or an electric radiator fan, consumes a large amount of electric power, the load on the alternator 10 suddenly increases. The increased load on the alternator 10 causes an increase in load on the engine, leading to a drop in engine speed. Consequently, at a low engine speed, as in the case of idling, for example, there has been a danger in that the engine undesirably stops.
To solve such a problem, there has conventionally been proposed, for example, incremental control of the alternator 10. According to the incremental control, even when the load on the alternator 10 suddenly increases, the operation of the alternator is not suddenly accelerated. Instead, the operation of the alternator is gradually accelerated in order to prevent the engine from stopping.
To be more specific, according to the incremental control, the field current supplied to the field coil 2 is gradually increased so as to avoid sudden acceleration of the operation of the alternator 10. However, carrying out the incremental control inevitably involves gradual increase in the number of monitor signals output to the FR terminal. This causes a delay in various types of control in the engine. For instance, a delay takes place in the control for increasing engine speed in response to an increase in the load on the alternator 10, leading to constant delay in response. This has been posing a problem in that the engine speed may gradually drop until the engine eventually stops.
Accordingly, the present invention has been made with a view toward solving the problem described above, and it is an object of the present invention to provide a voltage controller for an automotive alternator that is capable of avoiding a delay in response to an engine controller, thereby permitting proper engine control to be achieved.
To this end, the present invention provides a voltage controller for an automotive alternator, that includes a switching means connected to an alternator, which is driven by an engine to charge a battery, controls supply and cutoff of exciting current supplied to a field coil of the alternator and a conduction rate monitoring output terminal for monitoring the conduction rate of the field coil, wherein the conduction rate monitoring output terminal outputs the conduction rate of the field coil in a steady mode wherein the output voltage of the alternator is a predetermined voltage or more, while it outputs an alternator voltage change signal in a transient mode wherein the output voltage of the alternator is below the predetermined voltage.
Preferably, in the voltage controller for an automotive alternator, the conduction rate of the field coil is the conduction rate of a field coil driving transistor or an equivalent thereto, and the frequency is controlled to be a fixed value.
Alternatively, in the voltage controller for an automotive alternator, the conduction rate of the field coil is the conduction rate of a field coil driving transistor or an equivalent thereto, and is controlled to have an upper limit conduction rate and a lower limit conduction rate.
Alternatively, in the voltage controller for an automotive alternator, the conduction rate of the field coil is converted into a conduction rate signal of a predetermined frequency before it is output.
Preferably, in the voltage controller for an automotive alternator, the output of a conduction rate monitoring output terminal is controlled to have an upper limit conduction rate and a lower limit conduction rate.
Preferably, in the voltage controller for an automotive alternator, the switching means compares a battery voltage or a voltage equivalent thereto with a first set voltage thereby to control the supply and cutoff of exciting current supplied to a field coil, and the conduction rate monitoring output terminal outputs the conduction rate of the field coil if the battery voltage or the voltage equivalent thereto is not, less than a second set voltage, which is lower than the first set voltage, while it outputs a voltage change signal at a first set duty if the battery voltage or the voltage equivalent thereto is below the second set voltage.
Alternatively, in the controller of an automotive alternator, if the battery voltage or the voltage equivalent thereto drops below the second set voltage, then the conduction rate monitoring output terminal outputs a voltage change signal at the first set duty until the battery voltage or the voltage equivalent thereto exceeds a third set voltage, which is lower than the first set voltage but higher than the second set voltage.
Alternatively, in the voltage controller for an automotive alternator, if the battery voltage or the voltage equivalent thereto drops below the second set voltage, then the conduction rate monitoring output terminal outputs the voltage change signal at the first set duty for a predetermined period of time.
Alternatively, in the voltage controller for an automotive alternator, if the battery voltage or the voltage equivalent thereto drops below the second set voltage, then the conduction rate monitoring output terminal reduces an upper limit voltage of the voltage change signal.
Preferably, in the voltage controller for an automotive alternator, the first set duty is 100%.
Preferably, in the voltage controller for an automotive alternator, the switching means compares a battery voltage or a voltage equivalent thereto with the first set voltage thereby to control the supply and cutoff of exciting current supplied to the field coil, and the conduction rate monitoring output terminal outputs the conduction rate of the field coil if the battery voltage or the voltage equivalent thereto is below a fourth set voltage, which is higher than the first set voltage, while it outputs the voltage change signal at a second set duty if the battery voltage or the voltage equivalent thereto is the fourth set voltage or higher.
Preferably, in the voltage controller for an automotive alternator, if the battery voltage or the voltage equivalent thereto exceeds the fourth set voltage, then the conduction rate monitoring output terminal outputs the voltage change signal at the second set duty until the battery voltage or the voltage equivalent thereto drops down below a fifth set voltage, which is higher than the first set voltage but lower than the: fourth set voltage.
Alternatively, in the voltage controller for an automotive alternator, if the battery voltage or the voltage equivalent thereto exceeds the fourth set voltage, then the conduction rate monitoring output terminal outputs the voltage change: signal at the second set duty for a predetermined period of time.
Preferably, in the voltage controller for an automotive alternator, the second set duty is 0%.
Preferably, in the voltage controller for an automotive alternator, the conduction rate monitoring output terminal reverses an output signal and issues the reversed output signal.